Pial Synangiosis

Pial synangiosis is a type of surgery for moyamoya. It is the mainstay of surgical treatment in the Moyamoya Program at Boston Children’s Hospital. Pial synangiosis was developed and first performed at Boston Children’s in 1985. Since that time, the surgeons on our team have used this procedure to successfully treat about 50 children each year. Most children who have pial synangiosis are released from the hospital within a few days, and usually need only regular exams and monitoring as follow-up.

Pial synangiosis works by rerouting healthy scalp blood vessel to the brain, bypassing the narrowed vessels of moyamoya. This stimulates development of new blood vessels that grow from the donor scalp artery, providing a vital source of blood to the brain. The new blood vessels emerge not only from the transplanted scalp artery, but also from blood vessels sprouting from the coverings of the brain around the opening in the skull.

During the surgery, the neurosurgeon first makes an incision in the child’s scalp to expose a healthy blood vessel, called the superficial temporal artery.

The neurosurgeon then separates this artery from the surrounding tissue while blood continues to flow through it.

A window of bone is opened beneath the artery. The surgeon uses a microscope to carefully open each of the brain's coverings, exposing the surface of the brain.

The neurosurgeon then places the artery directly onto the brain and sews the tissues around it to the surface of the brain. This keeps the artery in direct contact with the brain. The neurosurgeon then replaces the window of bone and closes the incision in the skin.

The procedure usually takes three to four hours, but may be longer if both sides of the brain require surgery.

Based on our experience, about 4 to 7 percent of children will have a new stroke either at the time of surgery or within the first month after the operation. These strokes can range from mild to severe.

Most of the patients who had strokes during or after the procedure were already having serious neurological symptoms — including frequent strokes — in the weeks or months before surgery. We believe that patients with this type of history are at greater risk for stroke. For this reason, we typically wait four to six weeks after any stroke before proceeding with surgery. Nearly all patients who had a stroke during or after surgery have gone on to make excellent recoveries.